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class Link {
public int iData;
public Link next;
public Link previous;
public Link(int id) {
iData = id;
}
public String toString() {
return "{" + iData + "} ";
}
}
class DoublyLinkedList {
private Link first;
private Link last;
public DoublyLinkedList() {
first = null;
last = null;
}
public boolean isEmpty() {
return first == null;
}
public void insertFirst(int dd) {
Link newLink = new Link(dd);
if (isEmpty()){
last = newLink;
}else{
first.previous = newLink;
}
newLink.next = first;
first = newLink;
}
public void insertLast(int dd) {
Link newLink = new Link(dd);
if (isEmpty()){
first = newLink;
}else {
last.next = newLink;
newLink.previous = last;
}
last = newLink;
}
public Link deleteFirst() {
Link temp = first;
if (first.next == null){
last = null;
}else{
first.next.previous = null;
}
first = first.next;
return temp;
}
public Link deleteLast() {
Link temp = last;
if (first.next == null){
first = null;
}else{
last.previous.next = null;
}
last = last.previous;
return temp;
}
public boolean insertAfter(int key, int dd) {
Link current = first;
while (current.iData != key) {
current = current.next;
if (current == null){
return false;
}
}
Link newLink = new Link(dd);
if (current == last) {
newLink.next = null;
last = newLink;
} else {
newLink.next = current.next;
current.next.previous = newLink;
}
newLink.previous = current;
current.next = newLink;
return true;
}
public Link deleteKey(int key) {
Link current = first;
while (current.iData != key) {
current = current.next;
if (current == null)
return null;
}
if (current == first){
first = current.next;
}else{
current.previous.next = current.next;
}
if (current == last){
last = current.previous;
}else{
current.next.previous = current.previous;
}
return current;
}
public String toString() {
String str = "List (first-->last): ";
Link current = first;
while (current != null) {
str += current.toString();
current = current.next;
}
System.out.println("");
System.out.print("List (last-->first): ");
current = last;
while (current != null) {
str += current.toString();
current = current.previous;
}
return str;
}
}
public class MainClass {
public static void main(String[] args) {
DoublyLinkedList theList = new DoublyLinkedList();
theList.insertFirst(22);
theList.insertFirst(44);
theList.insertFirst(66);
theList.insertLast(11);
theList.insertLast(33);
theList.insertLast(55);
System.out.println(theList);
theList.deleteFirst();
theList.deleteLast();
theList.deleteKey(11);
System.out.println(theList);
theList.insertAfter(22, 77);
theList.insertAfter(33, 88);
System.out.println(theList);
}
}
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